1. Field of the Invention
The present invention relates to novel apparatus for moving a tool such as an ultrasonic transducer for treating an article of manufacture, as by welding parts together, sinking one part into another, rivetting over a plastic member, or boring a hole.
2. The Prior Art
Plastic parts such as film cassettes have been bonded together ultrasonically as described in U.S. Pat. No. 3,224,916. Ultrasonic techniques have also been used for the rivetting of plastic parts as in U.S. Pat. No. 3,367,809, and for sinking metal parts into plastic as in U.S. Pat. No. 3,184,353. Such operations require that an ultrasonic transducer having a horn be moved in one direction into contact with a workpiece where the ultrasonic vibrations, e.g., 20 KHz or more, cause softening or melting to accomplish the desired result. Then the ultrasonic transducer is moved in the opposite direction away from contact with the workpiece.
Movement of the transducer has been accomplished by a piston and cylinder mechanism in which the piston drives the transducer directly into and out of contact with the workpiece. Such a mechanism has been subject to certain disadvantages such as undesirably high impact against the workpiece, cylinder control problems related to acceleration and deceleration, loading of the transducer horn against the workpiece being dependent on cylinder pressure, follow-through of the horn after initial contact with the workpiece being dependent on piston follow-through, and the possibility of triggering ultrasonic power when the horn is unloaded resulting in potential damage to the horn. These disadvantages are most evident with systems using air as the fluid medium; high cycle speeds; large horns using long strokes; and high ultrasonic power.